Treatment of carbonaceous materials



Patented Sept. 29, 1936 TREATMENT OF CARBONACEOUS MATERIALS Mathias Pier,

Heidelberg,

Germany, assig I101 to I. G. Farbenindustrie Aktiengesellschaft, Frankfort-on-the-Main, Germany N Drawing. Application June 2, 1934, Serial No. 728,677. In Germany June 8, 1933 2 Claims.

The present invention relates to the thermal treatment of carbonaceous substances.

In the cracking of liquid carbonaceous materials, such as tars, mineral oils and their distillation and conversion products, in the absence of added hydrogen, which treatment includes the distillation under splitting conditions, an attack on the inner parts of the apparatus which come into contact with the hot materials under treatment frequently takes place. Furthermore trouble in the operation of the apparatus is caused by excessive formation of coke.

I have now found that the said drawbacks can be avoided to a great extent by wholly or partly a providing at least the parts of the apparatus which come into contact with the hot distillable carbonaceous materials under treatment, i. c. with the materials having a temperature above 150 0., more particularly those having a temperature above 200 C., with a superficial alloy of zinc and iron, preferably an alloy containing between 10 and 90 per cent by weight of zinc.

' The said alloy consists of a thin layer, preferably having a thickness of up to 1 millimeter, and may be prepared by thermal treatment. For ex ample an iron apparatus to be coated with the zinc alloy may be embedded in zinc powder and heated, or immersed in molten zinc, or sprayed with zinc and then heated, preferably at temperatures of from 400 to 800 C., if desired in the presence of gases, which do not chemically attack the zinc at these temperatures, such as hydrogen, nitrogen or carbon dioxide. The production of the superficial alloy of zinc and iron may also be effected by exposing the necessary parts of the iron apparatus, to an atmosphere of zinc vapor While excluding oxygen, at temperatures above the melting point of zinc but preferably below 900 C. for a long period, for example about 50 hours. For example the articles to be coated may be introduced into a vessel containing zinc and capable of being closed, the zinc being vaporized after closure. There may also be passed through the vessel containing zinc a slow current of an inert or, preferably, a reducing gas, any penetration of oxygen into the vessel being prevented by keeping the gas passed through at a higher pressure than the outer atmosphere. The necessary zinc vapor may also be produced in a special zinc vaporizing apparatus. By suitable selection of the Working temperature and duration of treatment it is possible to influence the zinc content and thickness of the superficial layer according to desire. In many cases it is advantageous that the material which has first been treated with zinc vapor at high temperature, as for example 800 0., should then be treated for a long period, for example about 50 hours, at a lower temperature, as for example at 600 C. The apparatus may consist of iron, steel or an alloy steel. It is preferable to provide not only the reaction chamber but also the preheater, regenerator and inlet and outlet conduits with the said coating.

The coating of iron-zinc alloy may also be applied to the desired parts of the apparatus by any other suitable means, for example by dipping the apparatus into a molten iron-zinc alloy or applying the alloy in the form of powder onto the apparatus and then heating and the like. In this case the apparatus need not be constructed of iron, steel or an alloy steel. It is, however, preferable to employ such apparatus of iron, steel or alloy steel and producing the coatings of iron-zinc alloy by the action of the hot zinc or zinc vapor on the iron in the apparatus of iron, steel or alloyed steel.

The advantage of the process according to this invention resides in the fact that on the one hand the inner parts of the apparatus withstand the injurious action for example of the vapors and gases formed during the cracking of tars and petroleums even after working for long periods, and on the other hand the formation of coke is considerably less than when working in the apparatus usual in cracking processes.

The employment of such apparatus is also eminently suitable for chemical reactions with carbon monoxide, for example for the preparation of metal carbonyls such as iron carbonyl. By reason of the fact that hydrogen is not present or is only present in a subordinate degree, it is not necessary to employ material immune to hydrogen.

The following example will further illustrate the nature of this invention but the invention is not restricted to this example.

Example An American petroleum containing 4 per cent of sulphur is treated in a cracking apparatus at 500 C. under a pressure of '70 atmospheres. The apparatus consists of iron, and the parts which come into contact with the hot reaction materials are coated with a zinc alloy. The alloy is prepared for example by charging the pipe with a mixture of 25 parts by weight of zinc powder and 75 parts by weight of ground alumina and then heating it for about 50 hours to 900 C. in a chamber from which air is excluded. By the said treatment the zinc vapor penetrates into the surface of the iron and forms a thin layer of an alloy of zinc and iron. Zinc vapor produced in a special vessel may also be led, while excluding air, over the surfaces of the apparatus which are to be treated, the desired alloy thus being formed' Even after using the apparatus for long periods of time, no appreciable attack by sulphur is noticeable.

What I claim is:-

l. A process for the cracking of liquid carbonaceous materials at a high temperature and MATHIAS PIER. 

